It is known to incorporate phosphate groups into polycarboxylate polymers used as water-reducing agents for concrete and other hydratable cementitious compositions.
In JP-A 11-79811, Hamada et al. disclosed a copolymer obtained by polymerizing a monomer having a sulfonic or phosphoric acid group, a monomer having an oxyalkylene group, and a monomer having a carboxylic acid group. It was described that the copolymer acted to reduce the water while otherwise maintaining the fluidity of concrete.
In JP-A 2000-327386 A1, Shoichi et al. disclosed a cement-dispersing polymer obtained by polymerizing a monoester or mono-ether, a polyalkylene glycol, and a monomer having a phosphoric acid group.
In U.S. Pat. No. 7,470,733, Shirota et al. disclosed the use of a phosphoric monoester having an alkyl ether group and a phosphoric di-ester having both alkyl ether and mono-ester groups, wherein the polymer had a monoester/monoester+diester ratio of 0.4 to 0.95. This characteristic purportedly imparted an excellent viscosity-reducing effect in the concrete.
In US Patent Application Publ. No. 2006/0293417 A1, Taniguchi et al. disclosed a two-polymer dispersant having improved viscosity-reducing effect. Polymer A contained carboxylic acid groups and oxyalkylene and/or oxystyrene groups, possibly including copolymers of a specified “monomer 1,” namely, an ethylene unsaturated carboxylic acid derivative having a polyoxyalkylene group, and a (meth)acrylic acid group (“monomer 2”). Polymer B also contained “monomer 1” but further included a monophosphate group (“monomer 3”) and diphosphate group (“monomer 4”).
In US Patent Application Publication No. 2008/0035022 A1, Hamada et al. disclosed a phosphate polymer for improving fluidity and reducing viscosity of concrete. The polymer was obtained by copolymerizing a monomer having a polyoxyalkylene group (“monomer 1”), a phosphoric monoester (“monomer 2”), and a phosphoric diester (“monomer 3”) at pH 7 or less. It was noted however that the phosphate monomers were obtained as a mixture of monoester and diester groups and were difficult to employ in cements. Hamada et al. copolymerized the monomers in a manner to suppress cross-linking and explained that the molar ratio of monomer 1 to monomers 2 and 3 was preferably 5/95 to 95/5 and more preferably 10/90 to 90/10 (See “[0099]”). The molar ratio among monomers 1, 2, and 3 was preferably 5-95/3-90/1-80, and, more preferably, 5-96/3-80/1-60 (total=100). The molar ratio and mol percentage of monomers 2 and 3 were calculated on the basis of the compound in the acid form (See “[0099]”). The molar ratio of monomer 2 (phosphate monoester) to monomer 3 (phosphate diester) could be 99/1 to 4/96, and more particularly 99/1 to 5/95 (See “[0101]”).
In US Patent Application Publication No. 2009/0258969 A1, Shimoda et al. disclosed a method for producing a phosphoric acid, ester-based polymer, which included copolymerizing the following monomers: (1) an ethylene unsaturated carboxylic acid derivative having a polyoxyalkylene group; (2) a monoester phosphate-based monomer; and (3) a di-ester phosphate-based monomer. The polymer could be obtained by copolymerizing monomers 1, 2, and 3 at pH 7 or lower in the presence of a phosphonic acid-based chelating agent. Alternatively, the polymer could be obtained by mixing a solution containing monomers 1, 2, and 3 at a temperature of 10 to 50 degrees C., initiating a polymerization within 72 hours after mixing, and by maintaining this temperature until polymerization is initiated.